The overall objective of this proposal is to characterize human tumor and normal tissue blood flow during local hyperthermia induced by 915 MHz microwaves. Tumor blood flow should be the most important parameter in determining the effectiveness of hyperthermia because it is the primary mode of heat transport, often limiting the temperature achieved to less than 42.5 degrees C, as well as the primary mode for the transport of drugs, oxygen, and nutrients to the tumor. While tumor blood flow has been studied in heated animal tumors, the techniques employed are generally unsuitable for human experimentation. As a consequence, little data exists on blood flow in heated human tumors. This proposal addresses the determination of blood flow in heated human tissue by measurement of the rate of thermal clearance when the microwave power is turned off, and the determination of blood flow before or after heating by use of a thermal dilution probe. Data will be generated to investigate the spatial distribution of tumor blood flow, changes in blood flow during heating, the magnitude of tumor blood flow as a function of tumor type, volume, and temperature, and changes that occur in tumor blood flow throughout the treatment regimen. A possible reduction in tumor blood flow after the cessation of heating will be investigated and the ratio of tumor to normal tissue blood flow will be determined.